High penetration of wind turbines in the electrical grids has let requirements for the wind turbines, on how they should contribute to the stability of the electrical grids, such requirements are included in so-called grid codes.
One of the requirements which may be included in certain grid codes is inertia response. Inertia response is a functionality where the power is boosted from the normal production for a short period of time, i.e. power delivered to the electrical grid is increased. The boost of power function may be available at all wind speeds, for very low wind speeds, the power boost may be rather reduced.
Depending on the grid code, the details of the boost phase may vary. In some locations a boost power should be provided upon request. In an example it may be specified that whenever the production from the wind power plant is above 25% of rated power, the wind power plant has to be able to deliver a power boost of 5-10% of rated power for a given time period, e.g. up to 10 seconds. The grid code may also specify requirements for the recovery period. As an example, after the boost it may be specified that the turbine must have returned to normal operation after 2 minutes, and that during the recovery phase, the power produced by the wind turbine should remain within 80% of available power.
Many of the boost power methods known from the prior art suffer from various elements such as complex calculation algorithm, transient behavior when the wind turbine goes from partial-load wind conditions to full load conditions, and not at least difficulties during the recovery phase.
The present invention provides a solution to circumvent at least some of the problems with the prior art.